This invention relates to an apparatus and process for producing a foam suspension of liquid and air in a continuous flow liquid dispensing system.
Commercial cleaning fluids, e.g., for bathroom tiles, appliances, and the like, are dispensed from aerosol containers in which a propellant produces a continuous flow of liquid upon the actuation of a valve. Cleaning fluids can also be delivered from manual pulsating or pumping systems which deliver discrete amounts or pulses of the liquid upon an operator manually actuating a lever. This invention concerns only the continuous flow type of system
The cleaning fluid dispensed by such systems often contains a powerful solvent which, while effective in removing grease and other contaminants, is extremely repugnant to the olfactory senses and eyes of the user. It has been determined as a part of the present invention that the odor and irritation level of a liquid constituent is a direct function of the degree of liquid atomization or aerosolization. That is, the smaller the liquid particulate suspended in the spray issued by the dispensing device, the more the liquid is atomized and subject to being sensed by the olfactory faculties of the user. The larger the liquid particulate size, the less odor and irritation will be sensed by the user.
Prior art systems for dispensing liquid cleaner solutions have produced liquid streams which "bounce off" the target surface (e.g., bathroom tile or the like) with consequent liquid wastage and loss of control of stream direction.
In such prior art systems, another problem has been that while a stream is moving towards the target surface, there is a continuous or periodic "dribble" of fluid immediately proximate the exit of the dispensing device.
It has been determined that one way to eliminate liquid dribbling and "bounce back" from the target surface is to produce a mixture of air and liquid particulate in the form of a "foam." Liquid dispensed in aerated foam form has been found to adhere better to a target surface and to reduce the tendency for bounce. In the prior art, however, there has not been a system which concurrently solved the aforementioned problems while increasing the particulate size, thus reducing the vapor phase of the liquid constituent to reduce odor and irritation to the user.
The present invention utilizes a "flow interrupter" which produces aerated foam by "impingement" thereof on a continuous flow liquid stream. The system is arranged so that a continuous flow of liquid is issued in a diverging spray pattern from a flow orifice. A sharp edged interrupter structure is introduced into a controlled portion of the periphery of said diverging spray of liquid such that only a controlled percentage of that periphery impinges upon the interrupter and is made to change direction with consequent turbulence. The center of the stream, inside the periphery, is not impeded and retains full energy for maximum spray distance. The turbulence created where flow reversal occurs at the stream periphery causes a drop in pressure which produces an in-flow of ambient air in a direction opposite to that of the main liquid stream.
The ambient air mixes with the liquid stream not only at the immediate areas of turbulence but also downstream of the interrupter such that the entire liquid stream becomes a low velocity, thoroughly mixed, air-liquid foam system which issues from the exit point of the apparatus.
The liquid product which issues from the apparatus contains relatively large particles of liquid in suspension with air for reduced olfactory irritation and sensation. Further, the particular design of the interrupter of the instant apparatus prevents agglomeration of liquid particulate at the point of exit so as to eliminate liquid dribbling or errant spray direction.
Numerous attempts have been made in the past for providing at least certain aspects of the advantages achieved by the present invention. For example, U.S. Pat. No. 3,946,947 to Schneider discloses a prior art method for producing foam in an atomized spray. Schneider teaches the utilization of a venturi throat downstream of a spray orifice and also downstream of a plurality of air inlet passages. In the known fashion, passage of the atomized stream through the venturi throat reduces the pressure in the throat and causes suction of air through air inlet ports which are upstream of the venturi with consequent mixing of the air and fluid in the venturi. Schneider does not teach liquid particle size management or downstream turbulence creation and air induction for creating foam.
Another example of a prior art attempt to produce foam is shown in U.S. Pat. No. 4,219,159 to Wesner. This patent discloses a rather complicated device which provides several restricter means and an impingement "screen" downstream of a spray orifice and also downstream of air inlet passages similar to the invention taught by Schneider. The Wesner apparatus provides an intermittent or pulsated flow which produces a "pumping action" for drawing in upstream air between the spray orifice and a downstream disposed flow restricting screen.
In contradistinction to the prior art systems, the present invention comprises a simple apparatus and process for interrupting only the outer periphery of an atomized spray cone so as to interfere with, only the relatively small sized liquid particles found at the periphery and to cause turbulence of only those particles to produce air induction from a source downstream of the means for interrupting the peripheral flow.